Laser airborne remote sensing real-time acquisition, processing, and control system

The U.S. Air Force Phillips Laboratory is evaluating the feasibility of long-standoff-range remote sensing of gaseous species present in trace amounts in the atmosphere. Extensive system integration in the laboratory and an airborne test are leading to remote sensing ground tests and airborne missions within the next year. This paper describes the design, external interfaces, and initial performance of the Laser Airborne Remote Sensing (LAPS) acquisition, processing, and control system to be deployed on the Phillips Laboratory NC-135 research aircraft for Differential Absorption Lidar (DIAL) system performance tests. The dual-CPU VME-based real-time computer system synchronizes experiment timing and pulsed CO, laser operation up to 30 Hz while controlling optical subsystem components such as a laser grating, receiver gain, mirror alignment, and laser shutters. This real-time system acquires high rate detector signals from the outgoing and return laser pulses as well as low rate health and status signals from the optical bench and the aircraft. Laser pulse and status data are processed and displayed in real time on one of four graphical user interfaces: one devoted to system control, one to remote mirror alignment, and two other interfaces for real-time data analysis and diagnostics. The dual-CPU and multi-layered software decouple time critical and non-critical tasks allowing great flexibility in flight-time display and processing.